Boundary acoustic wave devices are compact and possess excellent temperature stability because no hollow package is required and because silicon oxide is utilized as a temperature compensating film.
WO98/52279 discloses the relation between the Q value, and theta, and film thickness of polycrystalline silicon film in a boundary acoustic wave resonator for leaky boundary acoustic waves including an IDT, silicon oxide film and a polycrystalline silicon film on a substrate mainly of lithium niobate piezoelectric single crystal cut out in a theta-rotated Y cut, and set with the X axis as the acoustic wave propagation direction (abbreviated hereinafter to theta YX-LN single crystalline piezoelectric substrate). Also disclosed is that an aluminum nitride film can be utilized instead of the polycrystalline silicon film.
Japanese Patent Application Laid-Open Publication No. 10-84247 discloses the relation between propagation loss and theta in a boundary acoustic wave device for leaky boundary acoustic waves, including an IDT, silicon oxide film, and single crystalline silicon on a theta YX-LN single crystalline piezoelectric substrate.
WO2005/069485 and WO2006/114930 disclose acoustic boundary devices that have small boundary acoustic wave propagation loss.
The non-patent document, “A method for estimating optimal crystal cuts and propagation directions for excitation of piezoelectric surface waves” (J. J. Campbell and W. R. Jones, IEEE Trans. Sonics and Ultrason., Vol. SU-15 (1968) pp. 209-217) reports on a method for estimating acoustic boundary wave propagation loss.